1. Field of the Invention
Apparatuses consistent with the present invention relate to a high resolution autostereoscopic display, and more particularly, to a high resolution autostereoscopic display apparatus in which resolution is not decreased and cross talk does not occur as an image is displayed in an interlaced method.
2. Description of the Related Art
An autostereoscopic display apparatus is used to display an image for the left eye and an image for the right eye that exhibit binocular parallax respectively to the left and right eyes of a viewer. The viewer can view a 3-D image by recognizing the left eye image and the right eye image provided by the autostereoscopic display apparatus through the retinas of both eyes. Autostereoscopic display apparatuses include apparatuses using a parallax barrier method and apparatuses using a lenticular method.
According to the parallax barrier method, the images that are to be viewed by the left and right eyes are alternately displayed in a vertical pattern and the displayed images are viewed using a very thin vertical grid, that is, a barrier. In this way, the vertical pattern image for the left eye and the vertical pattern image for the right eye are divided by the barrier so that images of different view points are viewed by the left and right eyes, thus forming an autostereoscopic image. Also, as illustrated in FIG. 1, a related art lenticular type autostereoscopic display apparatus includes a display panel 11, alternately displaying image signals for the left and right eyes, and a lenticular sheet 12, installed in front of the display panel 11, which separates the images for the left and right eyes.
However, since the images for the left and right eyes are simultaneously displayed by a single display panel 11 for the above related art lenticular type autostereoscopic display apparatus, the resolution of a stereoscopic image viewed by a user is reduced to ½ of the original resolution of the display panel 11. Also, in order to enable a switching action between a 2-D image mode and a 3-D image mode, a very complicated additional structure is needed.
Thus, a time-sharing type autostereoscopic display apparatus has been developed that can provide a stereoscopic image without a decrease in the resolution, using a high speed responsive liquid crystal display (LCD) having a refresh rate of 120 Hz.
For example, Japanese Patent Publication No. 2004-325494 discloses an autostereoscopic display apparatus having a display panel, an image separating unit, and a light deflecting unit. In the related art autostereoscopic display apparatus of the above mentioned publication, the display panel periodically shifts, by a pixel, the left and right images that are alternately displayed. A related art image separating unit such as a parallax barrier arranged on the front surface of the display panel separates the left and right images that are alternately displayed by the display panel. At this point, the light deflecting unit that is periodically shifted in synchronization with the left and right shift period of the display panel deflects an image for the left eye to the left eye and an image for the right eye to the right eye. With such an autostereoscopic display apparatus, since the positions where the images for the left and right eyes are displayed switch at a high speed, a user hardly notices any degradation in resolution. However, there is a problem in that the light deflecting unit formed of ferroelectric liquid crystal is very expensive and the loss of light due to the parallax barrier is high.
U.S. Pat. No. 5,969,850 discloses an autostereoscopic display apparatus 20 which includes a backlight unit 21, a spatial light modulator 22, a lenticular lens sheet 23, and a high speed responsive LCD display panel 26, as illustrated in FIG. 2. The spatial light modulator 22 is formed of a plurality of left eye and right eye cells 24 and 25 that switch between a transparent state and an opaque state according to the ON/OFF state of power. In the autostereoscopic display apparatus 20, the high speed responsive LCD display panel 26 alternately displays the images for the left eye over the whole screen in a very fast time period. The spatial light modulator 22 switches the cells 24 and 25 in synchronization with the left and right image switching time of the high speed responsive LCD display panel 26. For example, while the high speed responsive LCD display panel 26 displays the images for the left eye, the spatial light modulator 22 switches the left eye cell 24 to a transparent state so that the light emitted from the backlight unit 21 is directed only towards a left eye viewing zone 28 of a user. Also, while the high speed responsive LCD display panel 26 displays the right eye image, the spatial light modulator 22 turns on the right eye cell 25 so that the light emitted from the backlight unit 21 is directed only towards a right eye viewing zone 27 of the user. In a conventional 2-D mode, all the left eye and right eye cells 24 and 25 of the spatial light modulator 22 are turned on.
However, in the time-sharing type methods of the above-discussed Japanese publication and U.S. patent, cross talk is generated between the left eye image and the right eye image so that the user is not able to view an accurate 3-D image. In general, most display panels sequentially scan an image of a frame from the top of a screen to the bottom. While an image of a previous frame is displayed on the lower side of the screen, an image of the subsequent frame is displayed on the upper side of the screen. For example, when the period for the complete scanning of a frame is T, as illustrated in FIG. 3, a right eye image is displayed in the whole screen at a time “0” and a left eye image is displayed in the whole screen at a time “T”. However, since the right eye image continuously changes into the left eye image between the time “0” and “T”, the left eye image is displayed on the upper side of the screen while the right eye image is displayed on the lower side of the screen. As a result, there is a time that the left eye image and the right eye image share the screen. Thus, as in the time-sharing type method U.S. patent, when the left eye and right eye cells 24 and 25 of the spatial light modulator 22 are simply turned on and off alternately, the left eye image and the right eye image are not completely separate and sensed by the left and right eyes of a user at the same time.
Also, the above-described Japanese publication and U.S. patent have a problem of using an expensive high speed responsive LCD display panel in order to prevent a flickering phenomenon. In order to prevent the flickering phenomenon, a related art autostereoscopic display apparatus can display an image at a scanning speed of about 50-60 Hz or more. For the above described autostereoscopic display apparatuses, as illustrated in FIG. 4A, at an instant, an image is only viewed by the left eye while no image is viewed by the right eye. Also, as illustrated in FIG. 4B, at another instant, an image is only viewed by the right eye while no image is viewed by the left eye. As a result, when a conventional LCD display panel having a vertical scanning speed of about 60-75 Hz is used, the flickering phenomenon is generated since the left and right eyes can view an image that is displayed at a scanning speed of 30-37.5 Hz. Thus, the conventional LCD display panel having a vertical scanning speed of 60-75 Hz cannot be used for the related art time-sharing type autostereoscopic display apparatus.